1. Field of the Invention
This invention relates to a shaft furnace having a metal shell, a refractory lining and cooling bodies projecting through the shell into the lining, the cooling bodies being arranged for cooling liquid, e.g. water, to flow through them during operation of the furnace. The invention is especially applicable in a case where, at least adjacent each of the cooling bodies, the lining consists of a refractory material of coefficient of thermal conductivity (.lambda.-value) of at least 10 kcal/mh.degree.C. All .lambda.-values are determined at 20.degree. C.
2. Description of the Prior Art
Shaft furnaces, in particular blast furnaces, of the above type are known and can have the advantage of high uniformity of temperature in the lining. In U.S. Pat. No. 3,953,007 there is described for example a construction in which cooling plates which are located around the furnace in a horizontal plane are always in direct thermal contact with an annular graphite construction in the lining. This effects a uniform temperature distribution in the lining, in spite of the fact that the cooling plates transfer heat locally outside the lining. This uniformity of temperature distribution throughout the lining appears to be very favourable to the achievement of a long life of this lining.
Cooling bodies, e.g. plates, extending through the lining also function as anchors which help to prevent breaking away or shifting of the lining.
As remarked, the high coefficient of thermal conductivity of materials such as graphite and semi-graphite has advantages. More particularly, the use of graphite in lining constructions for shaft furnaces is also advantageous because of the high thermal shock resistance of this material. Among other things, this is associated with a much lower coefficient of thermal expansion and a higher strength at high temperatures than conventional refractory materials for blast furnace linings such as fire-brick. The construction described above initially can offer considerable advantages by virtue of its having a longer life than other lining constructions. The availability of the furnace is higher and the repair costs lower.